According to state regulations, heating subsidies are distributed in Ningxia, Shanxi, Shaanxi, Shandong, Hebei, Qinghai and Tianjin. That is, the northern region, excluding Shanghai.
It's not too cold in Shanghai. It's four to six degrees below zero at the coldest time, so the water won't freeze. So Shanghai uses electric heaters to keep warm after air conditioning in winter.